Esophageal cancer is a highly aggressive malignancy and is the sixth leading cause of cancer death worldwide. There are two main types of esophageal cancer, esophageal squamous cell carcinoma (ESCC) and adenocarcinoma. This project focuses upon the elucidation of molecular mechanisms underlying early events in malignant transformation in the esophageal squamous epithelium. Epidermal growth factor receptor (EGFR) overexpression and p53 mutation are frequent genetic alterations in the premalignant stages of esophageal squamous cell carcinogenesis. Yet, the molecular basis for EGFR's and mutated p53's contributions to esophageal carcinogenesis remains unclear. To that end, the biological roles and functional consequences of EGFR overexpression and p53 mutation will be determined in vitro and in vivo. Our proposed studies will use esophageal epithelial cells and mouse models with targeted overexpresssion of EGFR and mutant p53 in the esophagus to determine the role of these genetic alterations in ESCC. Our fundamental hypothesis is that ligand activation of EGFR induces cellular responses that facilitate hyperproliferation in the basal cell compartment and induction of migration of such cells into the suprabasal compartment without commitment to differentiation. Although, these processes are necessary they are not sufficient to cause cancer, and thus, other genetic events, such as p53 mutation, are required. This hypothesis will be pursued by the following interrelated Specific Aims: Aim 1: To assessthe consequences of the combination of EGFR overexpressionand p53 inactivation in esophageal epithelial cells. Esophageal epithelial cells overexpressing EGFR and four diffent mutant p53s will be characterized when grown in monolayer, and three-dimesional Matrigel and organotypic culture. Studies will test effects on proliferation, migration and invasion capabilities as well as effects on key signaling molecules. Aim 2: To understand the in vivo roles of the cooperation of EGFR and mutant p53 using mice (cre-lox system) expressing EGFR and mutant p53 in the esophagus. Studies will attempt to generate two novel in vivo models of ESCC by expressing human EGFR and mutant p53 specifically in the esophagus. Over 14,000 new cases of esophageal cancer were diagnosed in the United States last year. It is estimated that more than 90% of those diagnosed will die of their disease. The proposed studies aim to provide novel insights into the biological roles of EGFR overexpression and p53 inactivation in the development of ESCC. Ultimately, these may translate into newer diagnostic and therapeutic modalities.